Hard to say what symptoms a non-motorcraft IAC will do, wandering idle for sure, stalling maybe
3rd party use stepper motors, they are great, and Ford did start to use them for EGR valves, but they don't react well with Fords Pulse width modulation(PWM) setup used for IAC Valves
Stepper motors are like a "digital" motor, they will rotate a certain degree based on voltage input, and that moves the IAC valve in and out, and its very accurate, but not what Ford uses, lol, many other car makers do use it
Ford uses a magnetic field to pull the valve open or let the spring close it, a solenoid setup, PWM varies the voltage to hold idle at "target" RPM constantly varying the voltage slightly to maintain the "target"
A stepper motor needs a set voltage and it will turn to that point in its rotation and stay there until voltage changes
Solenoid moves based on voltage and voltage can vary a bit without too much of a reaction
Ford computer "Learns" the IAC voltage needed, say 7.0v for 750rpm, and 6.9v or 7.1v is OK as well
On a stepper motor 6.9v, 7.0v and 7.1v are different positions
And it will drive the computer "nuts" as it tries to learn/adjust RPMs when the stepper motor is so "jumpy", its not as fluid as solenoid operation
PWM is just not the correct electrical system to use with stepper motors